What is the cause of abnormal noise from CBB capacitors?

CBB capacitors are also one of the electronic components commonly used by engineers, and are generally used in circuits with high requirements.

With being well-known and widely used, in the process of practice, we have encountered some unavoidable small problems, why use CBB21, capacity, withstand voltage 400V, 200 50Hz

Actually, this is the case because of the harmonics in the circuit.

Today's power grids contain a variety of higher harmonics, mainly in the form of electric current, and capacitors like to interact with them, if someone nearby uses electric welding, or thyristor phase-modulated high-power appliances, the electrodes of the capacitor will vibrate and make a sound.

In addition, the harmonic current has a great destructive effect on the capacitance, the electrode of the CBB capacitor is a metal film sprayed on the film, and the part close to both ends is easy to generate ohmic heat under the action of instantaneous high current, which causes the film to melt and cause a short circuit.

Because the thermal conductivity of the film is small, the instantaneous local temperature rise inside cannot be judged by the external temperature rise, so it is best to check the manufacturer's specifications, which should have a limit on the wave current, and the unit should be the current time product, such as by second, by millisecond, etc.

It is also possible that the current is too large and is not caused by the current limiting resistor.

The capacitance** is definitely not low.

The overall circuit volume is not necessarily smaller than that of a power frequency transformer with the same capacity.

In addition to the factors caused by the circuit, the quality of its CBB capacitance is also very important.

If you encounter a capacitance that is too low, you need to consider it carefully.

If you do not add CBB capacitance, only the junction capacitance of the rectifier tube remains, which is very small, once the loop has stray inductive reactance, its resonant frequency is very high, the amplitude is very large, one is easy to break down the rectifier tube, and the other is EMI deterioration. The reason for choosing CBB capacitors is the advantage of **, and the withstand voltage is secondary; Second: because the capacitor has to withstand a high enough surge charging current, the CBB capacitor with a "self-healing" effect is selected.

Self-healing effect: The surge charging current will cause the capacitor capacity to become smaller, but the CBB capacitor can withstand it, and the capacity loss is relatively small!

The self-healing principle of CBB capacitor is: when there is a problem or click on the medium of CBB capacitor, the metallization coating at the breakdown point or the problematic position will volatilize instantaneously under the action of the arc, so that the poles of the capacitor will form a short circuit again and resume normal work.

The internal discharge is in, and the capacity will become smaller and smaller, or it will break down completely.

It means that the voltage at both ends is too high, or the quality is not good.

If the capacitor is touched by the shutdown hand, it will heat up, indicating that the capacitor has a problem and will be damaged after a long time.

The reasons for capacitor damage: first, the quality of the capacitor itself; Second, the working voltage is higher than the withstand voltage value of the capacitor; The third is to work under high temperature conditions for a long time due to external force or long-term work.

1. Deal with the abnormal operating conditions in time, and find abnormal conditions such as bulging belly, joint heating, and serious oil leakage (leakage) of the shunt capacitor during operation, and it must be withdrawn from operation. For malignant accidents such as fuel injection, oil injection, and other malignant accidents, a power outage inspection should be carried out immediately, and the cause of the accident should be ascertained and dealt with before replacing the new capacitor to continue operation.

2. Strictly control the operating voltage, and the operating voltage of the shunt capacitor must be strictly controlled within the allowable range. That is, the long-term operating voltage of the shunt capacitor shall not be greater than 10% of its rated voltage value, and the operating voltage is too high, which will greatly shorten the service life of the capacitor. With the increase of operating voltage, the dielectric loss of the shunt capacitor will increase, which will increase the temperature of the capacitor, accelerate the aging speed of the capacitor insulation, and cause premature aging and breakdown of the insulation in the capacitor.

In addition, under the action of excessive operating voltage, the insulating medium inside the capacitor will undergo local aging, the higher the voltage, the faster the aging, and the shorter the life.

3. Fuse protection should be installed for each single capacitor, and the rated current of the fuse shall not be greater than the times of the rated current of the protected capacitor, so as to avoid the occurrence of group explosion accidents caused by failure of a capacitor due to the failure of a capacitor in time.

4. When the shunt capacitor is disconnected correctly, due to the arc action between the static and dynamic contacts of the switch, it will cause the operation overvoltage, in addition to the requirement that the capacity of the switch is about 35% larger than the capacity of the shunt capacitor bank, it must also be a circuit breaker with high insulation recovery strength, small arc reignition and good arc extinguishing performance between the contacts.

5. Control the operating temperature, in a normal environment, it is generally required that the temperature of the hottest spot of the shunt capacitor shell shall not be greater than 60, otherwise, the cause must be found out and treated.

6. Strengthen inspection, inspection and maintenance of shunt capacitors should be checked regularly for power outages, at least once a quarter, mainly to check whether there is dust and other dirt in the capacitor housing, porcelain sleeve, mounting bracket and other parts, and clean carefully. During the inspection, special attention should be paid to whether the connection of each connection point is firm and loose; Whether the shell is bulging, oozing (leaking) oil, etc. If the above phenomena are found, the capacitor must be removed from operation and properly disposed of.

CBB capacitor daily inspection items: 1. Check whether it is operating under the rated voltage and rated current, and the indication value of the three-phase ammeter should be balanced. 2. The casing is completely clean, and there is no crack or discharge.

3. The terminals of each connecting wire should be tight, not loose and free of heating. 4. There is no deformation and expansion of the shell. 5. There is no abnormal sound inside the capacitor.

6. There is no flashover outside, and the shell is grounded intact. 7. The capacitor room should be well ventilated, and the operating environment temperature should not exceed 45. 8. The protection devices of the capacitors are all put into operation accordingly.

9. Check that the circuit breaker, transformer, reactor, discharge coil, etc. of the capacitor should be normal. Through reactive power on-site compensation, line loss can be reduced; Reduce line voltage drop and improve voltage quality; Improve the power supply capacity of the system. Zhixu JEC specializes in manufacturing safety capacitors, varistors, monolith capacitors, CBB capacitors, polyester capacitors, high voltage capacitors, and more quality capacitors in JEC.

Capacitors are mainly used for filtering.

CBB capacitors have good high-frequency characteristics, good filtering effect, and small size. The medium is a solid electrolytic capacitor, and the medium is the electrolyte.

Filters can be used, depending on the occasion, usually choose the ones that can be substituted for each other.

This capacitor acts as a current limiter.

Isn't it, can it still limit the current after the 4007 rectification? Do you see if it's skewered or combined? Or what, it's better to post a picture if you have a picture.

It is recommended that you carefully read the following inverter manuals before doing so.

The user manual of any brand of inverter should be clearly marked: capacitive load cannot be added behind the inverter, which of course includes capacitors.

The capacitive load will release electrical energy after the inverter stops, and the released electrical energy will be applied to the inverter module of the inverter, resulting in the damage of the inverter module.

Capacitor heating and cable scorching should be caused by too much harmonic content in the output of the inverter. Because the output of the inverter contains a large number of higher harmonics, these harmonic voltages are very high, when the harmonic voltage continues to challenge the withstand voltage value of the capacitor, then the capacitor heating is too normal.

Polypropylene capacitors (CBB).

Capacitance: 10p--10

Rated voltage: 63--2000V

Polarity: None.

The capacitor should have a ringing sound, or there is a temperature, it is abnormal, once found, there is no need to replace it, and when he is not good, other things that should not be broken may also be broken. It is recommended to replace it as soon as possible to avoid the expansion of the fault.

1. If there is a capacitance test gear on the multimeter, measure it directly.

When we dial the capacitance test gear, the red pen is connected to the positive pole and the black pen is connected to the negative pole. If there is infinity, it means that the capacitor is open and leaked; When it is measured to zero, it indicates that it has been broken down. The presence of a number in the normal range indicates normal.

2. Indirect measurement.

a. Capacitance resistance test method.

This method is suitable for detecting small capacitances below 10pf, and can only qualitatively check whether there is leakage, internal short circuit or breakdown. When measuring, you can choose to use the multimeter R 10K block, and use the two meter pens to connect the two pins of the capacitor at will, and the resistance value should be infinity. If the measured resistance (the needle swings to the right) is zero, it means that the capacitor is damaged by leakage or internal breakdown.

b. Check the quality of the electrolytic capacitor in the diode file of the digital multimeter.

This method is suitable for cases where the electrolytic capacitor is broken down. Put the digital multimeter in the diode file, connect the two meter pens to the two ends of the electrolytic capacitor, and pay attention to listen at this time, whether the digital multimeter emits a "dididi" sound, if not, it proves that it is good and has not been broken down.

How to measure CBB capacitance with a multimeter.

Measuring the capacitance of 400V105J with a multimeter can only measure the quality of the capacitance in the low voltage state, because the highest battery used in the multimeter is only 15V, so it can only measure the state below the battery voltage. Above some voltages, the capacitance may have problems such as breakdown, increased leakage current, etc., which cannot be measured with a multimeter. Accurate measurements require the help of specialized instruments.

In the actual repair process, alternative inspections are usually used.

If you see the pointer swinging first and then slowly coming back, it means that the capacitance is good, and the multimeter can not measure the capacitance value (the digital meter can).

The multimeter can measure the capacitance value and measure the value.

You can't just measure the resistance, if it's infinite, it's good, and if it's not the other way, it's bad.